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Thank you for answer I didn't think about rel canonical, great advice!

The obvious answer (but not necessarily the correct one) is you lost some important links pointing to your website somewhere. This would cause a drop in your metrics, and could cause a corresponding drop in your organic traffic. I might run a check with Majectic to look at your historic backlink profile, and also Google Webmaster tools Impressions report, to see if it matches the drop in traffic you've found. Are you aware of any links that you've lost? You can comb through your referrer data in Google Analytics to see if any good sources suddenly dried up in the weeks/months leading up to the drop. On the other hand, it could all be coincidence. The drop in DA could be a random event caused by the Mozscape crawlers simply missing an important set of links, which happens occasionally. And the drop in rankings could be due to an algorythm change (Check the Google Algo Update History to see if any of the dates match up) If you find any missing links, you can work to regain them. Otherwise the only way back is probably to build new, better links. Hope this helps! Best of luck with your SEO!